In dental restoration, a prosthetic is prepared to replace one or more missing, damaged, or unaesthetic looking teeth. Such dental prosthetics include bridges, full crowns and partial crowns. Full and partial crowns are supported by remaining portions of the original tooth or teeth and/or by an abutment and/or dental implants extending from the jaw bone. Bridges are supported by two or more teeth structures adjacent to the missing teeth or solely by implants that replaces the missing tooth root.
The dental prosthesis is generally for functional and aesthetic purpose is made of porcelain, the porcelain is a brittle material and to withstand the occlusal forces it need reinforcing. The reinforcing is generally obtained from a core structure of a hard material such as metals, aluminas (al2o3) zirconium, lava and more core material known to the art. The core structure is then incrementally covered with increments of porcelain slurry made of liquid and porcelain powder to provide outer surface of a tooth that is shaped according to the location in the mouth of the one tooth or more teeth. The surface of restoration is than tooled to provide the outer surface of the restoration in accordance with the appearance of a tooth. Since the preparation of the prosthesis, including the tooling of the prosthesis is performed at a dental laboratory; neither the recipient nor the dentist has any control on the final appearance of the restoration. Due to this situation, the recipient and the dentist expectations often do not adhere with the final appearance of the prosthesis, this lead to dissatisfaction and redo of the restoration to please the patient anticipations.
One prior art method involved building a wax model of the proposed restoration and receive the recipient approval. The drawbacks of this method are: (I) The dentist usually can propose very limited options that are in the boundaries of his artistic capabilities expertise and cost; (ii) The method is a time consuming; (iii) The shade of the teeth are not included in this method, the wax do not demonstrate the shade of the porcelain; (iv) the success of this method depends on the technician's capabilities to copy the teeth structure that was approved by the recipient and the dentist.
However, also in this case, the preparation of the prosthesis, including the tinting of the prosthesis material, is performed at a dental laboratory and neither the recipient nor the dentist has any control on the final appearance of the prosthesis. Thus, also in this method of dental restoration, the recipient is often is not satisfied with the final appearance of the prosthesis.
A computerized manufacturing machine can be used to produce dental ceramic prosthesis or prosthesis core that provides strength and support to the overlying glass ceramic.
The glass ceramic can be applied to the computerized manufactured core by way of layering increments of wet powder (layering technique), when the prosthesis receives a general larger shape of the designated tooth it is to be sintered in a furnace achieving 700-1000 C to become a solid porcelain tooth.
The prosthesis can then be manually shaped (with burs on a rotary machine) to the obtain the final shape, then it is glazed with glass powder and sintered to receive a glossy finish. This technique requires high skills of the dental ceramists and requires long labor time (about 20-120 minutes per prosthesis unit).
Another possible way to overlay glass ceramic to the computerized (cad cam) manufactured core would be using lost wax or using digital cad cam grinded cavity tooth like shaped technique and then press technique. It is noted that this method has limitation, as the aesthetic is poor due to use of one shade porcelain. In order to improve aesthetics it is required to add translucent porcelain at the outer surface of the prosthesis using the layering technique and sinter this by a time consuming procedure. In addition the strength of the outer surface is reduced.
Another method is the making of single or more units when the cad cam machine makes the complete one or more crown.
These methods suffer from various drawbacks such as: (i) The production of the prosthesis is time consuming; (ii) the dental prosthesis is mono chromatic and as such, lacks the natural appearance aesthetic features, (iii) the core material is manufactured by costly computerized manufacturing centers, (iv) the cost of the manufacturing of a full shaped teeth is high due to the high cost of the milled blank ceramic block and the milling itself, and (v) a milling key adds more costs to the dentists and patient.
There is a growing need to improve the restoration process and especially to increase the predictability of the restoration process.